This invention relates to air conditioning systems in general, and specifically to a mobile air conditioning system that uses ambient air as the refrigerant and excess engine heat as a comfort heat source.
The conventional vehicle passenger air conditioning system, broadly defined to include both cooling and heating of the interior air, uses two closed systems, both of which depend, directly or indirectly, on the operation of the internal combustion engine. The air cooling system is a closed cycle, refrigerant vapor compression system that typically includes a compressor, a condenser, an expansion device, an evaporator and a refrigerant reservoir. These components are connected by means of suction, discharge, and liquid lines to form a closed, sealed system through which the refrigerant flows. The most common refrigerant is now R-134a, chosen within the last few years as a non ozone damaging alternative to the prior chlorinated fluorocarbons. Because the system is closed and sealed, air for the passenger spaced is cooled indirectly by blowing it over the evaporator, concurrently warning the refrigerant in the evaporator, which is cycled back to the compressor to be compressed, cooled in the condenser, expanded by the expansion device and then routed back to the evaporator to complete the cycle. The air heating system is another closed system, but is not pressurized. A portion of the heated, liquid coolant is diverted and pumped from the internal combustion engine cooling system, routed to heat exchanger called a heater core, and vehicle interior air is blown over it. The evaporator and heater core and generally packaged within one housing, the air heating and cooling systems are essentially independent.
While the newer R-134 refrigerant is ozone friendly, it is still considered a so called xe2x80x9cgreenhouse gas,xe2x80x9d that is, a gas that absorbs heat more readily than pure air. Pure air, of course, has no such greenhouse potential, by definition, and could be used directly in a passenger comfort system, rather than indirectly, potentially eliminating at least the evaporator. Ambient air is also cost free and readily available, and can be used at low pressure, unsealed system, all of which make it an attractive alternative, if a workable, practical system could be devised for an automotive application.
Open air cycle air conditioning systems in other mobile applications, such as airplanes, are known. Unlike the vapor compression system, the air cycle system does not use a refrigerant, which undergoes phase change as it flows through the system. Instead it depends for its operation on the processes of compression and expansion of air. In a typical airplane, there is a ready availability of compressed air, which can be tapped directly off the main engine supercharger or jet engine compressor. This compressed air is then expanded in a cooling turbine to provide chilled air for comfort cooling and pressurization of the passenger cabin. There is no such gratuitous supply of compressed air in a conventional automobile or truck, and, therefore adaptation of the air cycle air conditioning to such an application is not so straightforward. Moreover, the ambient temperature and humidity levels for a land-based vehicle are significantly more unfavorable compared to those for an airplane at an altitude of about 20,000 ft. above sea level.
The subject invention discloses an air cycle system for a motor vehicle directed to both heating a cooling of the passenger air, and directed to either an internal combustion vehicle, or electric powered, or a hybrid of the two. While the preferred embodiment disclosed is an open air cycle system, or one in which the working fluid and the air delivered to the passenger space are the same, a closed air cycle system is also possible
The invention is also directed at taking advantage of additional features of the air cycle system such as instantaneous heating of the passenger compartment for comfort and defrosting and supercharging for internal combustion drive engines to increase efficiency.